The present invention generally relates to a method and composition for an aldehyde absorbing insert that absorbs aldehyde emitted from containers, including e.g. polyethylene terephthalate (xe2x80x9cPETxe2x80x9d) bottles, which hold a beverage or drink (e.g food product) or other environmentally sensitive products (e.g. pharmaceutical products). In one embodiment, the insert is in a form of a molded cover, including e.g. a screw cap, that is composed, at least in part, of the composition of the present invention. In an embodiment, the composition of the present invention may be in a form of an induction seal. In a further embodiment, the composition of the present invention may be in a form of a liner that has an exterior surface substantially conforming to at least a portion of an interior surface of the container body. In one embodiment, the aldehyde absorber insert is composed of a composition having continuous interconnecting channel morphology comprising three componentsxe2x80x94two polymers (i.e. components A and B) and a particle (i.e. component C) wherein the channels consist mainly of component B and the majority of component C resides in the channels. Components A and B are generally immiscible within each other. In addition, one criteria for selecting component C and components A and B may be based on component C preferential affinity for component B over component A. Another criteria for selecting component C may be based on the capacity of component C to absorb aldehyde compounds. For example, component C may be a mixture of: (a) an earth alkaline oxide and/or alkaline oxide; and (b) a sulfite such as sodium metabisulfite.
Plastic materials offer the packaging industry many benefits including a degree of design flexibility. Specifically, polyethylene terephthalate (PET) has made significant inroads into bottling and packaging applications at the expense of the use of glass containers but primarily in applications where the needs for barrier properties are modest. An increased wall thickness is needed to improve the barrier properties of the container but has a negative impact on the economics of the container. The ratio of packaging material to package volume has typically limited PET bottles to multi-serve container uses for packaging of oxygen sensitive foods and beverages such as fruit juices and drinks. In addition, a container such as a bottle composed of plastic (e.g. PET) emits acid aldehyde volatiles that are absorbed by the liquid within the container and that may detrimentally affect the quality of the liquid including the taste and/or stability.
Moreover, when compared to traditional packaging materials such as glass and steel, plastics such as PET offer inferior barrier properties which limits their acceptability for use in packaging items that are sensitive to atmospheric gases, particularly when the exposure to the atmospheric gases will entail extended time periods. In response to this inferior barrier properties, the packaging industry has attempted to develop technology to improve the barrier properties of plastic containers by developing multi-layer containers that offer mixed polymer layers. These laminated packaging containers offer improved barrier properties but sacrifice many of the recycling benefits associated with single layer containers such as PET and polyethylene naphthalate (PEN) bottles. Furthermore, depending on the mixtures of polymers, copolymers, blends, etc., used in the layers, clarity of the layered container is often substantially diminished.
In addition, many containers are typically sealed either by a screw cap and/or an xe2x80x9cinduction sealsxe2x80x9d as an additional method of preventing oxygen ingress into the container. In one example, induction seals are generally composed of aluminum foil with a plastic sealant layer with adhesive. Ribbons of this foil/plastic lamination are used by the cap/lid makers to die-cut seals and friction fit them into the caps/lids. In high speed filling lines, once the containers are filled and the caps fitted with induction seals mounted on the container (e.g. bottles, jars, cartons), the containers pass through a radio-frequency tunnel. The radio frequency activates the adhesive on the induction seal liner and it adheres to the container""s access rim. In the case of bottles or cartons, the caps/lids are then tightened. In another example, the induction seal may be composed completely of a plastic material that is sealed by a conventional induction heating process.